Answer:
Small.
Step-by-step explanation:
This is really easy if you understand what an adjective is!
If you can use the word to describe something, then it is probably an adjective.
You can say: a "small" circle;
But you cannot say: a "water" circle, or a "bowl" circle. It just doesn't make sense.
Adjectives are describing words that add details to an idea, a thing, or a person.